Separation of mixtures of primary aromatic amines



Patented June 7', 1932 nnomnmscnnnxuknma ALBERT xnenrnorn, or coLoeNE-MU nnnvr, GERMANY, AS- SIGNORS TO GENERALAmtnvn-s wonns, INC'., on NEW YORK; N: Y, A CORPORA; monxor'nmwmnn 7 SEPARATION, on mxrnnns or BRIMARY- AROMA-mo Arum is. A No Drawing. Application filed vlDecember 16; 192 9, SeriaLNoQ 414,565; and in; German yIlecemh er 17, 1928,,

The present invention relates to themanu facture of'pure aromatic amines of the benzene'or naphthalene series-by the separation of mixtures ofsuch-amino compounds or such l nuclear rorf nitrogenj substitution products thereof, asare ableto form saltswithhydrohalicacids. t p 1 The new process consists in fractionally separatingthe pure 'hydrohali'c acid salts of} the aromatic amines contained in the mix ture. These salts are obtained in good yieldsfrom the mixtures of the respective amino compounds by dissolvingthem-ixture, if desired; in an indifferent organic solvent in which. th'e'hydrohalicacid'salts of thesar'omatic amines are insoluble, such as benzene, toluene, 'ch-lorobenz'ene o-dichloroben' zene, tet'rahy'dronaphthalene,.; tetrachloromethane, trichloroethane, benzine the like, and passing-intothemi-xtureor solution, while stirring, a slow current of dry'hyd'ro'hal'ic acid gas, for example,hydrochloric acid gas: If nosolvent is used andthe aromatic bases are. solid-at normalftemperature it willbe necessary to heat the mil lrture unltil it, becfomes liquid previou'sto te' intro 'uction o the e et so a reassi na usii issfas salt ofthe stronger b'asesmzitiy be isolated from a w ra; thel'emaininglzlminesli wring or Further reci itation b "ine ans'of h drol i t mlxture G n l Spoken 1t chloric acid as yields a has salt of bn-iewill be-necessary that the amlnes are present w lower a Com un n in a fiquefid state no'matter Whether-this 90% which is added to the subsequent thatt-he crystals separated consistl of' m-xylidinehydrochloride. It is evident therefrom that a double decomposition of the p-xyli dine hydrochloride with the in xylidin e base h s occurred. The same'applies also to other isomeric amines.

The invention lowing exa thereto:

is illustrated by the rare ples without being restricted",

Example 1 w I 250 gramsof crude-qxylidine- (containing; about. 56% of the meta; compound), are dissolved in'about 7 50-10(10fccs; of; benzene and: into; thissolutionis passed; while stirring, (temperature'about 20. C.) a slow current of; dry hydrochloric acid gas, such as-is obtained, for example, in the chlorination; of benzene; Somewhat more hydrochloric acid ga's," is provided than is: required fen the saturation of I the" -m-Xylidi-ne present; The crystals fiormed are filtered with: suction,,-w'ashed'w-ith some-benzene an'd'driedi; -Accor.dingiz to; this method. of working there are obtained from 250 grams of crude Xylidine containing about- 56 meta compound: about 130 grams of is efl'ect'ed'by' heating them until they have fused, or by dissolving .them in a solvent as mentioned" above; Thehydrohalic acid" salts of the stronger bases separate first in" a crystallized form, which usually can be readily filtered? The mixture of jba'ses remaining is then further treated in the same are separated successively according to their basicity in the form salts. r

The new process may be demonstrated'by the following experiment? When finely divided, dry crystals of-p-xylidine' hydrochloride are stirred for a prolonged time-with a solution of a small excess of m xylidine' base inbenz'ene and'the' crystals are then thorou'gh'ly filtered off by suction, it willbe found manner until'the' individual basic'com'ponents of their hydrohalio acid charge ofthe crude materialjto be crystal]- lized. The separation of pure, ni-Xylidine in the form of the hydrochloride can thus be carried out inacon paratively simpleandinexpensive manner. Theoandfp-Xylid'ines remaining in the mother liquors fcanb'e sepe arated in the former thei'r'hydrochloric'acid salts in a 'simila'r'manner by further treat ment with hydrochloricacid' gas and purified by recrystallization in; the known manner. l q I Ewampleg 2'50fgra1ns of an artificial mixture ofequal 7 parts of asymmetric m-xylidine I 1.3"-'di methyl-t-aminobenzene) vand Vic. ln xylidine (1.3-dimethyL2-aminobenzene solved'in 750cos. of benzeneand a slow curarep- 'disp 7 into this solution,

rent of dry hydrochloric acid is passed into this solution, while stirring. The crystals formed are filtered off by suction, washed with some benzene and dried. The free base contains 96% of asymmetric m-Xylidine. About 86% of the original asymmetric mxylidine base is separated in the form of its hydrochloride in one operation. 7

Emample 3 250 grams of crude o-Xylidine (obtained from pure o-xylene) are dissolved in 1000 ccs. of benzene and a slow current of dry hydrochloric acid is passed into while stirring and cooling. The crystals formed are filtered 0E by suction, washed with some benzene and dried. The base set free from this salt contains about 90% of asymmetric o-Xylidine (LQ-dimethyl-laminobenzene). The LQ-dimethyl-S-ainino benzene can be separated from the mother liquor in the same manner by further treating it with hydrogen chloride gas Example 4 250 grams of crude'toluidine are dissolved in 1000 cos. of o-dichlorobenzene and a slow current of dry hydrochloric acid' gas is passed while stirring and cooling. The crystals formedare filtered off by suction, washed with some benzene and dried. Thebaseset free from this saltcontains of p-tol'uidine. On further passing in' the solution hydrochloric acid gas,-'an interme-' diate fraction rich in the para compound is precipitated. It may be added tothe next I crude portion to be treated. The remainder consists of o-toluidine, which can be isolated either as salt or as basein the known manner. y

' Example 5 Through a solution of a. mixtureof 75% of 6-chloro-2-amino-1-methylbenzehe and, 25%. of 4-chloro-2-amino-l-methylbenzene in dry gaseous hydrobenzene a current of chloric acid is passed until the increase of Weight corresponds to %parts of the quantity of hydrochloric acid necessary forthe complete neutralization. The separated hydrochloric acid salt is sucked oil and washed with benzene. It is an almost absolutely pure hydrochloric acid salt of V 6-ch10ro-2- amino-l-methylbenzene, From the filtrate the t-chloro-2-amino-1-methylbenzene can be easily isolated in the known manner.

Example 6- 250 grams of crude chloronaphthylamine are dissolved in about 1000 ccs. of benzene; through this solution a constant current of dry hydrochloric acid gas is introduced,

While stirring, in such anamount that about 20% of the starting material are separated inform of a hydrochloric acid salt. The crystals thus formed are sucked oil and this solution,

washed with some benzene. They contain the largest part of the and 1.5-chloronaphthylamine of the crude chloronaphthylamine. The mother liquor contains -1.8-chloronaphthylamine in a good state of purity which .can be isolated therefrom as a salt or base in the known manner. The temperature and concentrations 1n the solvents specified in the above examples can be varied within widelimits.

can also be combined with other separatlon and purification processes in the sense hereinbefore described.

By th1s process not only isomeric amines The process but also other aromaticamino compounds 80 can be separated fromone another, the term aromatic amino compound being intended to include the unsubstituted aromatic amines as well as such aromatic amlnes as are substituted in the nucleus or at the nitrogen atom, for example by halogen atoms, hydroxy groups, alkyl groups, aryl groups, carboxylic acid groups or the like in such a manner that they are still able to form salts with hydrohalic acids.

Therefore, ourinew process represents a technically simple and cheap method'of septhrough a llquefied .mixture of'primary amines of the aromatic series which are capable of forming salts with hydrochloric acid, separating the precipitating hydrochloric acid saltof the stronger base, and further the term a the alpha-naphthylamine subjecting the mother liquor to the same treatment until the individual .bases are separated successively according to theirbasicity.

2. The new process which comprises passing a current of dryhydrochloric acid gas through a liquefied mixture of primary amines of the naphthalene series which are capable of forming salts with hydrochloric acid, separating. the precipitating hydrochloric acid salt of the stronger base, and fur;

ther subjecting the mother liquor to the same treatment untilthe individual bases are separated successively according to their basicity.- 3. The new process which comprises passing a current ofdry hydrochloric acid through a solution of crude chloronaphthylamine in an indifferent organicv solvent, separating the precipitating I a-naphthylamine and 1.5- chloro-naphthylamine hydrochloride, and further subjecting the mother liquor to the same treatment until the other bases are separated successively according to their basicity.

4. The new process which comprises passing a current of dry hydrochloric acid gas through a liquefied mixture of primary amines of the benzene series which are capable of forming salts with hydrochloric acid, separating the precipitating hydrochloric acid tures.

EDUARD TSCHUNKUR. ALBERT KLAMROTH. 

